Cardiovascular disease frequently arises from the accumulation of atheromatous deposits on inner walls of vascular lumen, particularly the arterial lumen of the coronary and other vasculature, resulting in a condition known as atherosclerosis. These deposits can have widely varying properties, with some deposits being relatively soft and others being fibrous and/or calcified. In the latter case, the deposits are frequently referred to as plaque. These deposits can restrict blood flow, leading to myocardial infarction in more severe cases.
The assessment and subsequent treatment of cardiovascular disease often utilizes various imaging modalities to image the interior of the vasculature. These imaging modalities can include fluoroscopic imaging, optical coherence tomography (OCT) imaging, intravascular ultrasound (IVUS) imaging, and virtual histology intravascular (VH-IVUS) imaging, among others. Fluoroscopy uses x-rays to obtain real-time moving images of a structure or object. OCT uses reflected light to create depth-resolved images. IVUS utilizes ultrasonic echoes to acquire images of the blood vessel and surrounding area. VH-IVUS is an imaging technique that produces a color-coded map of the arterial vessel, wherein different histological constituents are assigned different colors.
While all these modalities are useful in their own way, they also have their limits, particularly when detecting certain features of interest. For example, conventional grayscale IVUS cannot be used to image a stent placed inside the vessel without considerable difficulty. In addition, conventional IVUS also cannot easily image luminal borders due to the presence of blood in the vessel. The limitations of these imaging modalities can hinder efforts to properly diagnose and treat cardiovascular disease.